I could see the information you're requesting to be of 'value' to a Homeowner. (At the same time, I could also seeing it as a deterant as well.) BUT, I think it's all for the better.
Well, from my experience, strictly speaking, there are external 'things' that WILL affect the value. Inherantly, most improvements add value but some just make 'sense' (not dollars.) It's important for EVERYONE (Contractor, Realtor, Homeowner, Buyer, etc., etc.) to realize that variables like the Neighborhood, Growth, Location-Location-Location, and so on will affect all this. So, where does that leave you???
You can certainly saturate yourself with information, then 'share' it with the 'concerned party(s)'. So w/o further ado, check out these links (which are just a few) to get you started: